Numerous attempts have been made in the past to provide a roast coffee product which has both an intense, persistent aroma and high extractability of the flavorful water-soluble constituents often referred to as brew solids.
It long has been known that the extractability of roast coffee (the amount of brew solids which can be extracted from a given weight of coffee from which a coffee brew is made) could be increased by grinding the coffee to finer particle sizes. However, roast coffee products ground to very fine grinds have bed-permeability characteristics which can inhibit the extraction of the water-soluble constituents due to bed compaction, pooling, channeling, etc. To avoid such brewing problems, it has been conventional to provide roast coffee ground to mixtures of variously sized particles, such as the traditional grinds of "regular", "drip" and "fine".
It also is known in the art that coffee's extractability can be enhanced in comparison to conventional coffee products by flaking roast and ground coffee. Roast and ground coffee is transformed into flaked coffee by roll milling the roast and ground coffee (see, for example, U.S. Pat. No. 1,093,362, issued Apr. 14, 1933 to R. B. McKinnis, and U.S. Pat. No. 2,368,113, issued Jan. 30, 1945 to C. W. Carter). An improved flaked roast and ground coffee of enhanced extractability of the water-soluble constituents is disclosed by F. M. Joffe in U.S. Pat. No. 3,615,677, issued Oct. 26, 1971, as well as a method for its production in U.S. Pat. No. 3,660,106, issued May 2, 1972 to J. R. McSwiggin et al.
The roll milling process and final product taught in the above-cited patents, however, do have certain limitations. One such limitation concerns flake thickness. The Joffe '667 patent teaches that thick flakes (i.e. 26-30 mils) are undesirable because of their high flake density and that flakes of intermediate thickness (8-25 mils) are preferred (Col. 8, lines 49-54). Indeed, Joffe teaches that to produce a roll milled coffee product having consumer acceptable tamped bulk density of 0.38 to 0.50 g./cc., and preferably of 0.42 to 0.48 g./cc., it is "essential" that the flakes have a thickness of 8 to 25 mils and preferably of 10 to 16 mils (Col. 8, lines 55-60). Flakes within this thickness range are disclosed as being less susceptible than other flakes to variable bulk density.
The roll milling process also can affect detrimentally certain roast and ground coffee attributes. The principal disadvantage is that flaking reduces the container aroma level of packaged coffee and affects the quality of the aroma. To minimize the aroma penalty exacted by flaking, several modifications in the roasting and processing of the coffee beans have been developed. For example, mixtures of conventional roast and ground coffee and of flaked coffee have been formulated (see, for example, U.S. Pat. No. 3,615,667 issued Oct. 26, 1971 to F. M. Joffe). However, such mixtures merely trade off increased container aroma intensity for increased extractability when conventional roast and ground coffee which has a higher aroma level is substituted for flaked coffee which has higher extractability.
The container aroma level of flaked coffee could be increased by the simple addition of a highly aromatized carrier oil such as is disclosed in U.S. Pat. No. 3,769,032, issued Oct. 30, 1973 to Lubsen et al. Such an addition, however, would undesirably increase the oil level of the coffee itself as well as any coffee brew made therefrom. Moreover, the aroma material from relatively large quantities of donor coffee must be collected in order to aromatize small quantities of flaked coffee.
Both the aroma retention and the extractability of roast and ground coffee are said to be enhanced by the fast roasting of coffee beans. U.S. Pat. No. 3,088,825 by H. H. Topalian and U. D. Luddington (1963) and U.S. Pat. No. 3,122,439 by R. V. MacAllister and C. H. Spotholtz (1964) disclose processes for the fast roasting of coffee beans. The MacAllister patent also discloses that such fast roasted beans can be flaked.
The container aroma concentration also can be enhanced by cold processing roast and ground coffee to produce a flaked coffee product. U.S. Pat. No. 4,267,200, Klien & Gieseker (1981) discloses that cold processing can provide an increase in the container aroma level of a thin-flaked coffee. After the coffee has been roasted and quenched in conventional manner it is cooled to -5.degree. to 5.degree. F. (-21.degree. to -15.degree. C.) and then ground. After grinding, the coffee particles are within the temperature range of 20.degree. F. to 40.degree. F. (-7.degree. to +4.5.degree. C.), and the temperature is held below 40.degree. F. (4.5.degree. C.) throughout the rest of the processing.
There are disadvantages to cold processing, however. One is that it is an expensive procedure and requires special refrigeration equipment. Another is that some flaked coffee which has been cold processed shows a significant decrease in bed permeability. Such decreases lead to unacceptably long drain times necessary to prepare coffee brews.
Thus, those skilled in the art of coffee processing frequently have been faced with the problem that enhancing or optimizing one attribute can be achieved only at the expense of another. If roast coffee beans are finely ground, the extractability of brew solids is improved, but the resulting coffee product has bed permeability problems and reduced brew clarity. Coarsely ground coffee, on the other hand, produces a coffee with excellent brew clarity and aroma, but which suffers from poor extractability. Milling roast and ground coffee will improve the extractability of the brew solids from the beans, but decreases the container aroma, unless additional steps are taken, steps which can be costly and produce problems of their own.
Given the state of the coffee processing art as described above, there is a continuing need for new and useful roast coffee products which provide high extractability of the flavorful coffee brew solids and which possess high container aroma levels. Accordingly, it is an object of the present invention to provide a milled roast and ground coffee product of increased extractability and enhanced container aroma.
It is a further object of this invention to provide a method of enhancing the container aroma impact of milled coffee which is not as expensive as cold processing.
It is a further object of this invention to produce a milled coffee which gives superior brew clarity when compared to "regular" "drip" or "fine" grind coffees.
It surprisingly has been discovered that the above objects can be realized and superior coffee products provided which exhibit extractability equivalent to drip grind, superior container aroma, and flake density and bed permeability comparable to conventional roast and ground and flaked coffees by coarsely grinding and lightly milling roast coffee beans under cool, as opposed to cold, temperatures to form thick particles of coffee of about 30 to about 40 mils with a coarse particle size distribution and a density of about 0.40 to 0.46 g./cc. Although conventionally processed roast and ground coffee with a similar particle size distribution would have poor extractability compared to standard vacuum coffees, the unique coffee product made by a combination of coarse grinding and light milling has extractability equivalent to or better than other roast and ground coffee products. In addition, in contrast to the teachings of the prior art, it has been discovered that container aroma can be heightened by grinding and processing roasted coffee beans which have been cooled and maintained at a temperature below about 65.degree. F. (18.degree. C.), preferably between 55.degree. and 65.degree. F. (13.degree. and 18.degree. C.). Surprisingly, decreasing the temperature to below 40.degree. F. (4.5.degree. C.), as disclosed in U.S. Pat. No. 4,267,200, does not significantly enhance the aroma further.